Cutting insert and rotary cutting tool

Abstract

A cutting insert includes an insert body portion and a plurality of projecting portions provided integrally with the insert body portion. The projecting portion includes a cutting edge and includes projecting portion upper and lower surfaces, two projecting portion side surfaces, and a projecting portion side end surface extending therebetween. In the projecting portion, a round corner surface extends between the projecting portion upper surface and the projecting portion side end surface. The cutting edge is formed so as to include a corner formed along an edge of the round corner surface and such that the projecting portion side surface serves as a rake face. The projecting portion is designed such that a length between the two projecting portion side surfaces is smaller than a diameter of an inscribed circle defined on the insert body portion.

What is claimed is: 
     
       1. A cutting insert comprising:
 an insert body portion comprising a body portion upper surface, a body portion lower surface located opposite the body portion upper surface, and body portion side surfaces extending between the body portion upper surface and the body portion lower surface, the insert body portion including an axis defined therein which passes through the body portion upper surface and the body portion lower surface; and 
 a plurality of projecting portions each comprising a cutting edge, each projecting portion provided integrally with the insert body portion at an outer position of the insert body portion in a direction orthogonal to the axis, 
 wherein the projecting portion comprises a projecting portion upper surface connected to the body portion upper surface, a projecting portion lower surface connected to the body portion lower surface, two projecting portion side surfaces each connected to the corresponding body portion side surface, and a projecting portion side end surface extending therebetween, and the projecting portion comprises a round corner surface formed thereon and extending between the projecting portion upper surface and the projecting portion side end surface, 
 wherein the cutting edge is formed along an intersecting ridge portion between the projecting portion side surface and each of the projecting portion upper surface, the round corner surface, and the projecting portion side end surface, so as to include a corner formed along an edge of the round corner surface and such that the projecting portion side surface serves as a rake face, 
 wherein the projecting portion is designed in such a manner that a length between the two projecting portion side surfaces is shorter than a diameter of an inscribed circle defined on the body portion upper surface; and 
 wherein all projecting portions on the cutting insert are identical to one another. 
 
     
     
       2. The cutting insert according to  claim 1 , wherein the length between the two projecting portion side surfaces is larger than a thickness of the insert body portion. 
     
     
       3. The cutting insert according to  claim 1 , wherein the insert body portion comprises a raised portion formed on the body portion side surface. 
     
     
       4. The cutting insert according to  claim 3 , wherein the raised portion is formed to appear hidden when the cutting insert is seen from a side opposite to the body portion upper surface. 
     
     
       5. The cutting insert according to  claim 1 , wherein the projecting portions are formed such that when the body portion upper surface of the insert body portion appears shaped like a polygon, the projecting portions are positioned at vertices of the polygon. 
     
     
       6. The cutting insert according to  claim 1 , wherein the projecting portions are formed such that when the body portion upper surface of the insert body portion appears shaped like a polygon, the projecting portions are positioned on sides of the polygon. 
     
     
       7. The cutting insert according to  claim 5 , wherein the body portion upper surface of the insert body portion is shaped substantially like a triangle. 
     
     
       8. The cutting insert according to  claim 6 , wherein the body portion upper surface of the insert body portion is shaped substantially like a triangle. 
     
     
       9. The cutting insert according to  claim 1 , wherein:
 each projecting portion is formed substantially plane-symmetrically with respect to a first plane (S) that extends so as to contain the axis of the insert body portion. 
 
     
     
       10. The cutting insert according to  claim 1 , wherein:
 the projecting portion side surfaces are inclined such that a length (L 2 ) between the projecting portion side surfaces belonging to a single projecting portion decreases with increasing distance from the cutting edge. 
 
     
     
       11. The cutting insert according to  claim 1 , wherein:
 each projecting portion is formed substantially plane-symmetrically with respect to a first plane (S) that extends so as to contain the axis of the insert body portion; and 
 the projecting portion side surfaces are inclined such that a length (L 2 ) between the projecting portion side surfaces belonging to a single projecting portion decreases with increasing distance from the cutting edge. 
 
     
     
       12. The cutting insert according to  claim 1 , wherein:
 none of the projecting portion side surfaces are visible in a top view of the insert body portion upper surface, and all of the projecting portion side surfaces are visible in a bottom view of the insert body portion lower surface. 
 
     
     
       13. A rotary cutting tool including a tool body with two end surfaces positioned opposite each other and each shaped substantially like a circle, an outer peripheral surface extending between the end surfaces, and a bore hole penetrating both end surfaces,
 wherein the cutting tool comprises an insert mounting seat provided in the tool body and configured in such a manner that the cutting insert according to  claim 1  is mounted in the insert mounting seat. 
 
     
     
       14. The rotary cutting tool according to  claim 13 , comprising a first insert mounting seat which is open in one of the two end surfaces and a second insert mounting seat which is open in the other of the two end surfaces. 
     
     
       15. A cutting insert comprising:
 an insert body portion comprising a body portion upper surface, a body portion lower surface located opposite the body portion upper surface, and body portion side surfaces extending between the body portion upper surface and the body portion lower surface, the insert body portion including an axis defined therein which passes through the body portion upper surface and the body portion lower surface; and 
 a plurality of projecting portions each comprising a cutting edge, each projecting portion provided integrally with the insert body portion at an outer position of the insert body portion in a direction orthogonal to the axis, 
 wherein the projecting portion comprises a projecting portion upper surface connected to the body portion upper surface, a projecting portion lower surface connected to the body portion lower surface, two projecting portion side surfaces each connected to the corresponding body portion side surface, and a projecting portion side end surface extending therebetween, and the projecting portion comprises a round corner surface formed thereon and extending between the projecting portion upper surface and the projecting portion side end surface, 
 wherein the cutting edge is formed along an intersecting ridge portion between the projecting portion side surface and each of the projecting portion upper surface, the round corner surface, and the projecting portion side end surface, so as to include a corner formed along an edge of the round corner surface and such that the projecting portion side surface serves as a rake face, 
 wherein each projecting portion is formed substantially plane-symmetrically with respect to a first plane (S) that extends so as to contain the axis of the insert body portion; and 
 wherein the projecting portion side surfaces are inclined such that a length (L 2 ) between the projecting portion side surfaces belonging to a single projecting portion decreases with increasing distance from the cutting edge. 
 
     
     
       16. The cutting insert according to  claim 15  wherein:
 none of the projecting portion side surfaces are visible in a top view of the insert body portion upper surface, and all of the projecting portion side surfaces are visible in a bottom view of the insert body portion lower surface.